教你用一行Python代码实现并行任务（附代码）

#Example.py
'''
Standard Producer/Consumer Threading Pattern
'''
import time 
import threading 
import Queue 
class Consumer(threading.Thread): 
  def __init__(self, queue): 
    threading.Thread.__init__(self)
    self._queue = queue 
  def run(self):
    while True: 
      # queue.get() blocks the current thread until 
      # an item is retrieved. 
      msg = self._queue.get() 
      # Checks if the current message is 
      # the "Poison Pill"
      if isinstance(msg, str) and msg == 'quit':
        # if so, exists the loop
        break
      # "Processes" (or in our case, prints) the queue item  
      print "I'm a thread, and I received %s!!" % msg
    # Always be friendly! 
    print 'Bye byes!'
def Producer():
  # Queue is used to share items between
  # the threads.
  queue = Queue.Queue()
  # Create an instance of the worker
  worker = Consumer(queue)
  # start calls the internal run() method to 
  # kick off the thread
  worker.start() 
  # variable to keep track of when we started
  start_time = time.time() 
  # While under 5 seconds.. 
  while time.time() - start_time < 5: 
    # "Produce" a piece of work and stick it in 
    # the queue for the Consumer to process
    queue.put('something at %s' % time.time())
    # Sleep a bit just to avoid an absurd number of messages
    time.sleep(1)
  # This the "poison pill" method of killing a thread. 
  queue.put('quit')
  # wait for the thread to close down
  worker.join()
if __name__ == '__main__':
  Producer()

#Example2.py
'''
A more realistic thread pool example 
'''
import time 
import threading 
import Queue 
import urllib2 
class Consumer(threading.Thread): 
  def __init__(self, queue): 
    threading.Thread.__init__(self)
    self._queue = queue 
  def run(self):
    while True: 
      content = self._queue.get() 
      if isinstance(content, str) and content == 'quit':
        break
      response = urllib2.urlopen(content)
    print 'Bye byes!'
def Producer():
  urls = [
    'http://www.python.org', 'http://www.yahoo.com'
    'http://www.scala.org', 'http://www.google.com'
    # etc.. 
  ]
  queue = Queue.Queue()
  worker_threads = build_worker_pool(queue, 4)
  start_time = time.time()
  # Add the urls to process
  for url in urls: 
    queue.put(url) 
  # Add the poison pillv
  for worker in worker_threads:
    queue.put('quit')
  for worker in worker_threads:
    worker.join()
  print 'Done! Time taken: {}'.format(time.time() - start_time)
def build_worker_pool(queue, size):
  workers = []
  for _ in range(size):
    worker = Consumer(queue)
    worker.start() 
    workers.append(worker)
  return workers
if __name__ == '__main__':
  Producer()

urls = ['http://www.yahoo.com', 'http://www.reddit.com']
results = map(urllib2.urlopen, urls)

results = []
for url in urls: 
  results.append(urllib2.urlopen(url))

from multiprocessing import Pool
from multiprocessing.dummy import Pool as ThreadPool

pool = ThreadPool()

pool = ThreadPool(4) # Sets the pool size to 4

import urllib2 
from multiprocessing.dummy import Pool as ThreadPool 
urls = [
  'http://www.python.org', 
  'http://www.python.org/about/',
  'http://www.onlamp.com/pub/a/python/2003/04/17/metaclasses.html',
  'http://www.python.org/doc/',
  'http://www.python.org/download/',
  'http://www.python.org/getit/',
  'http://www.python.org/community/',
  'https://wiki.python.org/moin/',
  'http://planet.python.org/',
  'https://wiki.python.org/moin/LocalUserGroups',
  'http://www.python.org/psf/',
  'http://docs.python.org/devguide/',
  'http://www.python.org/community/awards/'
  # etc.. 
  ]
# Make the Pool of workers
pool = ThreadPool(4) 
# Open the urls in their own threads
# and return the results
results = pool.map(urllib2.urlopen, urls)
#close the pool and wait for the work to finish 
pool.close() 
pool.join() 

# results = [] 
# for url in urls:
#  result = urllib2.urlopen(url)
#  results.append(result)
# # ------- VERSUS ------- # 
# # ------- 4 Pool ------- # 
# pool = ThreadPool(4) 
# results = pool.map(urllib2.urlopen, urls)
# # ------- 8 Pool ------- # 
# pool = ThreadPool(8) 
# results = pool.map(urllib2.urlopen, urls)
# # ------- 13 Pool ------- # 
# pool = ThreadPool(13) 
# results = pool.map(urllib2.urlopen, urls)

import os 
import PIL 
from multiprocessing import Pool 
from PIL import Image
SIZE = (75,75)
SAVE_DIRECTORY = 'thumbs'
def get_image_paths(folder):
  return (os.path.join(folder, f) 
      for f in os.listdir(folder) 
      if 'jpeg' in f)
def create_thumbnail(filename): 
  im = Image.open(filename)
  im.thumbnail(SIZE, Image.ANTIALIAS)
  base, fname = os.path.split(filename) 
  save_path = os.path.join(base, SAVE_DIRECTORY, fname)
  im.save(save_path)
if __name__ == '__main__':
  folder = os.path.abspath(
    '11_18_2013_R000_IQM_Big_Sur_Mon__e10d1958e7b766c3e840')
  os.mkdir(os.path.join(folder, SAVE_DIRECTORY))
  images = get_image_paths(folder)
  for image in images:
    create_thumbnail(Image)

import os 
import PIL 
from multiprocessing import Pool 
from PIL import Image
SIZE = (75,75)
SAVE_DIRECTORY = 'thumbs'
def get_image_paths(folder):
  return (os.path.join(folder, f) 
      for f in os.listdir(folder) 
      if 'jpeg' in f)
def create_thumbnail(filename): 
  im = Image.open(filename)
  im.thumbnail(SIZE, Image.ANTIALIAS)
  base, fname = os.path.split(filename) 
  save_path = os.path.join(base, SAVE_DIRECTORY, fname)
  im.save(save_path)
if __name__ == '__main__':
  folder = os.path.abspath(
    '11_18_2013_R000_IQM_Big_Sur_Mon__e10d1958e7b766c3e840')
  os.mkdir(os.path.join(folder, SAVE_DIRECTORY))
  images = get_image_paths(folder)
  pool = Pool()
  pool.map(creat_thumbnail, images)
  pool.close()
  pool.join()